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Crack Monitors - For the monitoring of cracks in buildings and civil engineering structures.

Most buildings crack at some time during their service life. Usually the cracks are of little consequence but they may be the first indication of a serious defect. Monitoring the changes in crack width across a crack helps determine the cause of cracking and what remedial work should be specified.

Crack monitor in use

So Why Monitor?

Cracks often appear in buildings and civil engineering structures.  It is usually a symptom of distress within the materials used in the construction. Sometimes the cracks are of little significance and are easily repaired. Other times the cracks are the first sign of a serious defect which may affect the functioning or stability of the building. 

Monitoring the changes in the width of the cracks over a period of time helps to diagnose the cause and severity of the crack.. 

There are two important reasons cracks need to be monitored when they’re detected:

1. Cracks can indicate serious defects that threaten a structure’s stability

Although most cracks don’t raise major concerns, some most definitely do.  Cracks can be major red flags that indicate a serious defect within the fabric of the building––one of the first signs of a more serious problem that needs to be addressed. 

2. Cracks that go ignored can devalue a property regardless of the threat they pose

In addition to very real safety concerns, the mere appearance of cracked walls and other surfaces can devalue a building and affect its insurability, not to mention open the door for lawsuits in more extreme situations. 

With this in mind, having the ability to assess and continuously monitor cracks when they appear is crucial.  To do this, engineers need a rigid methodology as well as tools capable of highly accurate measurements.

Initial inspection and surveying with crack gauges 

The first step to crack monitoring is an obvious one: locating the cracks. But proper inspection is more than simply finding them. It’s also important to note any patterns that appear in the cracks, the construction materials used around them, and the age of the cracks if you can determine it.  

With a rough conceptual model to work with, the next step is surveying the cracks’ present conditions using a Crack Width Gauge. 

As pictured above, simply select a location on the crack where the edges are relatively straight and parallel in order to get an accurate width measurement. Record the width, length, and location of each crack and add this data to your working conceptual model where you can see each crack in relation to each other complete with its measurement information.

Using the right tools to achieve accurate monitoring measurements 

After completing a crack survey, monitoring should begin as quickly as possible. The longer you can monitor a crack, the better you’ll be able to determine its cause. 

There are a variety of ways to monitor cracks depending on the nature of the cracks and their position on the structure:

Tell-Tale Crack Monitors

“Tell-Tale” crack monitors are the most common kind of monitoring device and are highly valued for their easy installation and use.  

The Tell-Tale crack monitor consists of two plates.  One plate is calibrated in millimeters and the other has a red cursor in the form of a cross. The two plates overlap and are pre-set at zero on the calibrated scale with four pre-set pegs.  

When the Tell-Tale is fixed in position across the crack, the four pre-set pegs are removed and the two plates are free to slide as the crack opens and closes. The amount and direction of movement is recorded by noting the position of the red cursor line relative to the scale on the plate below.

A record sheet is provided with each Tell-Tale. Every time the Tell-Tale is inspected, the position of the red cursor line relative to the grid can be copied to the record sheet. It is important to note the date the reading was taken.

Avonguard’s Standard Tell-Tale Crack Monitors and Concrete Crack Monitors are calibrated to provide 1.0mm resolution and 0.5mm interpolation––the level of accuracy needed to make reliable measurements. Even more accurate readings of 0.1 mm can be taken if a caliper is used. The jaws of the caliper are located on the monitoring spigots of the Tell-Tale and the reading taken and recorded on the record sheet. 

Tell-Tales are capable of monitoring the movement of a crack horizontally or vertically over a flat surface and are ideal for plotting the trends and direction of movement over time. After remedial work is completed. 

For larger cracks, which require even greater precision, Avonguard’s Plus Tell-Tale has a larger scale allowing for monitoring up to +/-25mm in the horizontal plane. In addition, it also features spigots allowing for even finer precision crack monitoring using digital or vernier calipers.

Corner Crack Monitors

Cracks commonly appear at the corner junctions between walls and require a slightly different piece of equipment.

Although they operate essentially the same as other kinds of Tell-Tale monitors, Corner Crack Tell-Tale Monitors use a hinged gauge that fits angles between 70 and 180 degrees. When used in pairs, it’s even possible to calculate movement in all three dimensions. 

Crack monitors are indispensable tools for those in charge of ensuring that buildings are structurally sound and safe to inhabit. 

When it comes to reliability and accuracy, it’s absolutely crucial to make sure you’re using the kinds of high quality equipment you can trust to deliver precision and reliable readings time after time.

 

Berntsen International, Inc.
  • 1-800-518-0934
  • All other countries:
  • +1-608-249-8549
  • PO Box 8670
  • Madison, WI 53708-8670
We accept VISA, Master Card, American Express and Discover Card.